<template>
  <div ref="dragBox" style="display: flex; width: 100%; height: 100%;">
    <slot></slot>
  </div>
</template>
<script>


export default {
  name: 'DragBox',
  props: {
    
  },
  data() {
    return {
    }
  },
  methods:{
    // 如果dragItem 没有定义宽度，则flex=1
    setDragItemFlex () {
      const dragBox = this.$refs.dragBox
      const childsLen = dragBox.children.length

      for (let i = 0; i < childsLen; i++) {
        const node = dragBox.children[i]
        if (!node.style.width) {
          // 如果没有定义宽度，则flex=1
          node.style.flex = 1
        }
      }
    },
    dragControllerDiv () {
      const resize = document.getElementsByClassName('resize') // 拖拽条
      // 循环为每个拖拽条添加事件
      for (let i = 0; i < resize.length; i++) {
        // 鼠标按下事件
        resize[i].addEventListener('mousedown', this.onMouseDown)
      }
    },
    onMouseDown (e) {
      this.resizeBox = e.target
      this.currentBox = this.resizeBox.parentNode// 当前盒子
      this.rightBox = this.getNextElement(this.currentBox)// 当前盒子的下个兄弟节点
      if (!this.rightBox) return
      this.curLen = this.currentBox.clientWidth
      this.otherBoxWidth = this.$refs.dragBox.clientWidth - this.currentBox.clientWidth - this.rightBox.clientWidth // 其他盒子的宽度
      // 颜色改变提醒
      this.resizeBox.style.background = '#818181'
      this.startX = e.clientX;

      this.currentBox.style.userSelect = 'none';
      this.rightBox.style.userSelect = 'none';
      
      document.addEventListener('mousemove', this.onMousemove);
      document.addEventListener('mouseup', this.onMouseup);
    },

    // 获取下一个兄弟元素的兼容函数
    getNextElement (element) {
      if (element.nextElementSibling) {
        return element.nextElementSibling
      } else {
        var next = element.nextSibling// 下一个兄弟节点
        while (next && next.nodeType !== 1) { // 有 并且 不是我想要的
          next = next.nextSibling
        }
        return next
      }
    },
    onMousemove (e) {
      const endX = e.clientX
      const moveLen = endX - this.startX // （endx-startx）= 移动的距离
      const curBoxLen = this.curLen + moveLen // resize[i].left+移动的距离=左边区域最后的宽度
      const rightBoxLen = this.$refs.dragBox.clientWidth - curBoxLen - this.otherBoxWidth // 右侧宽度=总宽度-左侧宽度-其它盒子宽度
      // 当最小宽度时，无法继续拖动
      if (curBoxLen <= 200 || rightBoxLen <= 200) return
      this.currentBox.style.width = curBoxLen + 'px'// 当前盒子的宽度
      this.resizeBox.style.left = curBoxLen // 设置左侧区域的宽度
      this.rightBox.style.width = rightBoxLen + 'px'
    },
    onMouseup () {
      // 颜色恢复
      this.resizeBox.style.background = '#d6d6d6'
      document.removeEventListener('mousedown', this.onMouseDown)
      document.removeEventListener('mousemove', this.onMousemove)
    },


  },
  mounted () {
    this.setDragItemFlex()
    this.dragControllerDiv()
  },

}
</script>
